1. Field of the Invention
The present invention relates to a computer program product, system, and method for data processing data units of a data storage unit.
2. Description of the Related Art
In certain computing environments, multiple host systems may configure groups of data often referred to as “data sets” in storage volumes configured in a storage system, such as interconnected storage devices, e.g., a Direct Access Storage Device (DASD), Redundant Array of Independent Disks (RAID), Just a Bunch of Disks (JBOD), etc., which are typically controlled by a storage controller coupled to the hosts and storage devices. Data sets which may contain a file or many files, are typically comprised of data units often referred to as “extents,” which typically may comprise data stored in groupings of smaller data units often referred to as “tracks.” The Z/OS® operating system from International Business Machines Corporation (“IBM”) has a Volume Table of Contents (VTOC) to provide to a host, information on data sets of extents configured in the volume, where the VTOC indicates to the host, the location of tracks, extents, and data sets for a volume in storage.
Various data processing tasks are frequently performed at a storage volume level. For example, to avoid loss of data, data stored on a volume (often referred to as a primary volume) may be backed up by copying it to another volume (often referred to as a secondary volume) frequently stored at another geographical location. Accordingly, in the event that data on the primary volume is lost due to data corruption, hardware or software failure, or a disaster which destroys or damages the primary volume, the backup data may be retrieved from the secondary volume.
In a typical volume level copying operation by a storage controller, all tracks allocated to the volume are copied, whether or not the tracks contain client data or metadata. In many storage systems, hosts have access to metadata stored in a VTOC identifying which tracks of a volume have been allocated to data sets and which tracks of a data set contain client data or metadata. Using host software, some analysis may be done to avoid copying unallocated areas of a volume or unused areas of a non-VSAM (Virtual Storage Access Method) data set. However, such VTOC metadata has typically not been readily accessible to the storage controller. Moreover, for VSAM data sets, both used and unused areas within the data set are typically moved by the host software.